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378
METALLURGY OF IRON" AND STEEL.
secured by using a softer steel in its unannealed state. A comparison of the natural and annealed bars of corresponding tensile strength in Table XV-A will give the results shown in Tables XV-B and XV-C.
SEC. XVb.—Effect of annealing on bars rolled at different temperatures.—These results show that the annealed bar has a very much lower elastic limit than a natural bar of the same ultimate strength, and oftentimes has less ductility. The difference between the Bessemer and open-hearth steels cannot be due to irregular
TABLE XV-D.
Effect of Annealing Acid Open-Hearth Rolled Steel Bars 2x%
inches.
		"""S IM			F^    ^	h			
		_rd o OB	tp		43  C8		43	o3	•
	<3		42 13	S	a a>	•a &	00 g	2'	V P.
	to	rt§,3ri	CD M	^5   .	•a ^	4J~M	ri n	<H	
									
	(8 QJ	"".iTSs	•S&d	ri	Pi	SP,	rtp,	«43'	33
	A .	O"*"* S ^	d-0^	o	^ 03	3 tn		Oc)	2
.		oo c?i:''ft •	%$%	S	cS'S   .	«dJ	Cj 43	Is	o .
Pi 1	0^	al»§S .3 on ft o O	SrSa a|3 <Q pfl	i a'	sij	!§! 4Sft5i	bfifl flg 5.9	dK rQ g V Pi	^fl d V I-H O
0	to		e	•'	P		H	M	W
	'	56000 to 60000	Usual	Nat. Ann.	58180 52828	89733 81677	80.42 80.75	61.90 60.63	68.4 60.5
I	g	C   12' P   085*							
		Mil, .50.	Dull red	Nat. Ann.	69857 51557	48037 83893	81.83 32.92	59.60 63.60	71.9 65.7
		80000 to 64000	Usual	Nat. Ann.	61703 54463	41985 80953	80.19 80.88	60.70 59.35	68.0 56.8
II	4	C   12- P   086'							
		' Mn, .48.    '	Dull red	Nat. Ann.	68585 55058	45213 86988	80.06 80.94	57.58 61.58	71.1 67.2
		72000 to 80000	Usual	Nat. Ann.	75688 66584	49155 87934	24.66 26.06	54.05 50.74	64.9 57.0
III	8	0 .24' P   052'							
		Mn, .77.	Dull red	Nat. Ann.	.78083 67058	53334 40843	27.41 26.50	52.28 53.41	68.3 60.2
finishing, since all the bars were rolled at the same time, and further experiments given in Table XY-D indicate that the same law holds good whether the metal is finished hot or cold.
In the bars which are finished at the usual temperature there is a loss in strength due to annealing of from 6000 to 9000 pounds per square inch, and a lowering in the elastic limit of from 8000 to 11,000 pounds. In the colder finished bars the loss in strength is from 8000 to 11,000 pounds, and the elastic limit is lowered from 8000 to 13,000 pounds. Thus in both cases the elastic limit is affected much, more than the ultimate strength, and the,